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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 09-10-11, 12:38 PM   #1
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matching BB Spindles and Cranksets to avoid rounded out loosened crankarms I am

me look like a dope for not being able to get this working reliably.

(and she even did this on a modern 10-speed Record crankset up. is it possible that someone's pedaling style can cause crank boits to loosen?)

Originally this is a Vitus frame with DT shifting Shimano 105 bits. I don't remember the original crankset I ran it on for years and years before passing it on to Julie.

The latest crankarm to detach (and undoubtedly be rendered useless since the alloy square slot would likely be rounded out.) was Shimano 600.

and then a Stonglight left arm did the same.

I am ready to start again but I don't want to destroy another crankarm, especially a nice one.
I have a box with about 30 BB sets and a whack of cranksets. (though I would rather not send her out on the street with Nuovo Record gear. )

I was told that the spindle shape has to match the crankarm hole, to ensure the snuggest fit.
Stick with Japenese BB to Japanese cranks? French to French? etc.?
But how the heck to I ensure that? especially since the country of origin of many of my BB are not marked (the cheaper ones in particular.)

Many thanks
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Old 09-10-11, 01:01 PM   #2
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Read this: Mixing standards wouldn't cause the problem.

I doubt her pedaling style would loosen things up either.

The usual problem is that the crank bolt or nut was not tightened enough. Once the arm starts rounding, it's done. If you're using used crank arms, they may already be irreparably damaged.
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Old 09-10-11, 01:04 PM   #3
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Did you torque the bolts correctly? That's probably the #1 cause of rounding them off as you describe and destroying them.

Sheldon has an article about mixing and matching ISO and J.I.S. bottom brackets and cranks:
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